The Holy Grail of fast food

The GPS knows. It's got a whole section on fast-food outlets. This is, after all, the US.

I scroll through the list as California flashes past the car windows - the truck stops, the high-rises, the distant mountains, the endless black stretches of car-studded bitumen. The usual suspects are there in front of me, the McDonald's and the KFC. But I'm after something different. The Holy Grail.

This will be stop No.4 on the great American fast-food tour, a tour born of hunger and one that's quickly been gathering pace. Culture comes in many guises and the one I've been immersing myself in lately is the easy, greasy kind. Fast food.

The US is its spiritual home. You might think you know all the American fast-food chains, but when you come here you realise you don't know the half of them. Like the radio station that's playing country and western stars no one has heard of outside their homeland, there are plenty of American fast-food favourites that never made it big on the world stage.

And I've been trying them. It began in desperation, when only a burger would do, and there was only a weird joint named Carl's Jr to visit. Soon after that it became a thing - how many unheard-of fast food joints could I try?

This isn't Super Size Me. I don't want to get fat and I don't want to judge the people who are. All I want to do is have a taste of what's on offer. Some would call it gluttony, but I call it culture.

The US is unfairly maligned for all sorts of reasons, and one of them is definitely the food. Sure, this might be the country that invented the concept of food challenges, of daring diners to eat mountainous burgers and several-kilo steaks. And no one else could have thought up the "turducken" - a turkey stuffed with a duck stuffed with a chicken. But that doesn't mean it's bad. Necessarily.

Watch the signs for restaurants flashing past outside. Carl's Jr. White Castle. Jack in the Box. Taco Bell. Arby's. Wendy's. What are these places? I want to find out.

First stop a few days ago was Carl's Jr. I had a pressing need for grease brought on by the previous night's pressing need for beer. I walked in expecting a whole new spin on the fast-food genre, a new range of oily, horrible things to explore. What I found were burgers.

You should see the drinks at Carl's Jr - they're huge. A regular Coke basically comes in a bucket. The burgers are standard fare, mine looking as though it was caught under someone's shoe before it made it into the cardboard container. I don't know who Carl is, but I do know he does a decent hangover cure.

A few days later, Jack in the Box came calling, because, well, it was there. Rather than the sort of surprise the name would suggest, Jack in the Box sells the same kind of stuff everyone else does. Same goes for Arby's, which I called into as well. Colourful menus, big burgers. Americana.

Pretty soon the novelty of the great fast-food tour was wearing off. It was becoming apparent that, rather than providing a fascinating insight into a misunderstood genre of food and the wonderful American people who enjoy it, all the tour was providing was the chance for a few extra holes in my belt to get some use.

But today will be different. It's the grand finale, and it's the reason I'm scrolling through the car's GPS menu as northern California bustles past outside. I want In-N-Out Burger.

Californians don't just like In-N-Out, they love it. Hollywood celebrities love it. Grumpy chefs such as Gordon Ramsay and Anthony Bourdain love it. It's an institution and it demands a visit. No tour would be complete without it.

Ping! The GPS has found an In-N-Out just down the highway. I set my course and pull into the car park of a drab shopping centre right in the middle of Nowheresville, USA.

The burger joint is packed. It's '50s diner style, with red pleather booths and plastic tables. The menu is refreshingly simple - you don't get happy meals here, or bunless mega-burgers, or faux deli-style snacks for those kidding themselves into "healthy choices". At In-N-Out, you get the choice of hamburger, cheeseburger, or double cheeseburger. That's it.

You get fries on the side. You get a soft drink in a laughably regular-sized cup. You get normally proportioned people dining there.

But the only thing that's important is the taste, and an In-N-Out burger trumps them all. I'm sitting there in the leather booth scarfing down simple meat, onions, salad and a bun, and it's all tasting so good.

I've saved the best for last. Now, I wonder if the GPS can find me a dietitian?

What has been the best fast food you've discovered in your travels (in the US or elsewhere)? Post a comment below.